🚀 Mastering JavaScript Promises for FAANG Interviews

A Complete Guide to Patterns, Internals & Polyfills (with Examples) JavaScript Promises aren’t just another async concept — in FAANG interviews , they are a playground for testing deep technical understanding. You’re not only expected to use Promises… You’re expected to rebuild them . Get Richa Gautam 🌷’s stories in your inbox Join Medium for free to get updates from this writer. Subscribe Subscribe This guide breaks down the most important Promise patterns you must master to crack high-level JavaScript interviews. 🔹 Pattern 1: Promise Basics Before you dive into polyfills or chaining, you must know how Promises behave. ✅ What is a Promise? A Promise is an object representing the eventual completion (or failure) of an asynchronous operation. 🔥 Three core states Pending — initial state Fulfilled — operation completed successfully Rejected — operation failed ⚡ Key Methods Promise.resolve(value) → returns a fulfilled Promise Promise.reject(error) → returns a rejected Promise 🔹 Pattern 2: